optional

American  

[op-shuh-nl] / ˈɒp ʃə nl /

adjective

1. left to one's choice; not required or mandatory.

   Formal dress is optional.

   Synonyms:

   voluntary, elective, discretional

2. leaving something to choice.

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optional British  

/ ˈɒpʃənəl /

adjective

1. possible but not compulsory; left to personal choice

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Other Word Forms

• nonoptional adjective
• nonoptionally adverb
• optionality noun
• optionally adverb
• unoptional adjective
• unoptionally adverb

Etymology

Origin of optional

First recorded in 1755–65; option + -al ¹

Example Sentences

In confusing situations the car will call on Waymo’s “fleet response” team of humans, asking them to choose which of several optional paths is the best one.

From Los Angeles Times

Insurance companies will still be required to fully cover all childhood vaccines on the CDC schedule, including those now designated as optional, according to the Department of Health and Human Services.

From Los Angeles Times

“Tipping is not optional, in my mind,” said Ezekiel.

From The Wall Street Journal

Like many colleges, Virginia Tech has seen a huge increase in applications since making SATs optional.

From Los Angeles Times

The big environmental benefits would come from additional funding pots - known as the scheme's optional and collaborative layers, he argued.

From BBC